Vehicles having a dump body typically employ a hoist. The hoist imparts a force on the dump body to tilt the dump body from a resting position to a dumping position. The ability of the hoist to impart a rotational force on a dump body dictates how much weight the dump body may hold. The greater the rotational force imparted by the hoist, the greater amount of weight the dump body may hold.
For example, FIG. 1 illustrates a typical hoist 10 employing a cylinder 12 coupled with a torque arm 14, and a lift arm 16 coupled with the torque arm 14. The lift arm 16 couples with a dump body 18 such that when the lift arm 16 moves, the dump body 18 also moves. During operation, the cylinder 12 moves in a direction defined by a directional arrow X, thereby imparting a linear force along direction X on the torque arm 14. The linear force causes the torque arm 14 to rotate, thereby creating a moment M1 about an endpoint 20 of the torque arm 14. The rotation of the torque arm 14 causes the lift arm 16 to generally move in an upward direction Y. As the torque arm 14 rotates, the lift arm 16 moves the dump body 18 from a first position (not shown) to a second position.
The hoist 10 creates two forces while moving the dump body 18: a linear force along the direction X and the moment M1. If it is desired to increase the rotational force imparted by the hoist 10 such as to increase the dump body 18 capacity, the linear force may be increased or the moment M1 may be increased independent of the linear force. The cylinder 12 imparts the linear force through hydraulic pressure. In particular, pressurized fluid is fed into a piston 22 of the cylinder 12, which causes movement of a shaft 24. The pressurized fluid imparts the linear force along the shaft 24, which is translated to the torque arm 14. Thus, if the pressure of the pressurized fluid increases, the linear force imparted by the pressurized fluid also increases. However, in some applications, there are pressure rating limits for the piston 22. For example, pressurized fluid may not be fed into the piston 22 at more than 3000 psi in a hydraulic application. Otherwise, various components of the piston, such as seals, or the like, may prematurely wear, thereby causing failure of the hoist 10.
Furthermore, the overall dimensions of the cylinder 12 and the piston 22 may be increased by increasing a diameter of both the cylinder 12 and the piston 22 such that more pressurized fluid may be fed into the cylinder 12. However, when the diameters of the cylinder 12 and the piston 22 are increased, an overall size of the cylinder 12 also increases. Thus, the cylinder 12 may interfere with components of vehicle implementing the hoist, such as exhaust components, drivetrain components, powertrain components, and the like.
The moment M1 acting about the endpoint 20 of the torque arm 14, may be increased independent of increasing of the linear force to increase rotational force. In order to increase the moment M1 independent of the linear force, a length L1 of the torque arm 14 may be increased. Nonetheless, increasing the length L1 of the torque arm 14 increases the overall dimensions of the hoist 10. Thus, the hoist 10, which typically resides within a chassis of a vehicle having the dump body 18, may interfere with other components of the vehicle, such as the exhaust system, the differential, the suspension, or the like, of the vehicle.
Accordingly, what is needed is a hoist that can impart greater rotational forces to a dump body. Moreover, the hoist should have compact dimensions, such that the hoist does not interfere with other components of a vehicle using the hoist.